Thermal hardening of rails



Aug. 16, 1966 R. H. BENNEWITZ ETAL 3,266,956

THERMAL HARDENING OF RAILS Filed NOV. 29, 1963 4 Sheets-Sheet l g0:

FIG. 3

INVENTORS ROBERT H. BENNEWiTZ 8 HARLAND R. HEDLUND BY A TTORNE Y g- 1966 R. H. BENNEWITZ ETAL THERMAL HARDENING 0F RAILS 4 Sheets-Sheet 2 Filed Nov. 29, 1963 INVENTORS HARLAND R. HEDLUND A TTORNEY Aug. 16, 1966 R. H. BENNEWITZ ETAL THERMAL HARDENING OF RAILS Filed Nov. 29, 1963 4 Sheets-Sheet 5 FIG. 4

' INVENTORS ROBERT H. BENNEWITZ 8 HARLAND R. HEDLUND ATTORNEY g 1966 R. H. BENNEWITZ ETAL 3, 6,956

THERMAL HARDENING OF RAILS 4 Sheets-Sheet 4 Filed Nov. 29, 1963 Fl 5 INVENTORS ROBERT H. BENNEWITZ a HARLAND R. HEDLUND ATTORNEY United States Patent 3,266,956 THERMAL HARDENING OF RAILS Robert H. Bennewitz, Chicago, IlL, and Harland R. Hedlund, St. Paul, Minn., assignors to Union Carbide Corporation, a corporation at New York Filed Nov. 2a, 1963, Ser. No. 326,722 17 Claims. (Cl. 148-131) This invention relates to thermal hardening of rails, and more particularly to the hardening of a selected zone in the ball of a railroad rail, to increase the service life thereof.

The greater tonnage and higher speeds of modern trains increase the abrasive wear and other deteriorating effects on railroad rails. Furthermore, such deterioration is further increased when the track is curved. Centrifugal forces transmitted through the wheels to the rails cause increased compression on the concave side of the higher rail, and increased shear on the top of both rails. Also, When as the wheels are keyed onto the axles, the inside wheel going a shorter distance rotates at the same speed as the outside wheel going a longer distance, causing an abrasion longitudinally of the rail. F or these reasons, the service life of the rails on curves in some cases is being shortened, to as little as six months.

It has been proposed to thermally harden the wear surface of a rail length the ends of which are fixed. However, when a portion intermediate such fixed ends is heated, the thermal expansion in a longitudinal direction is resisted by the cold metal ahead of and behind the heated zone. This results in an increase in the height and width of the metal in the heated zone, and consequent upsetting of such metal.

When such upset is quenched, there is no force to reduce the width and height of the upset metal, so that longitudinal shrinkage results. Such shrinkage, upon release of the rail causes a lifting of the ends of the rail, and a curvature which is concave when looking down on the rail.

It has been proposed to avoid this resultant concavity by arching to precamber the entire length of each cold rail, as a separate and distinct step before subjecting the rail to heat treatment. But this precambering is laborious, expensive, difficult to control and the results are not uniform or reliable.

It is therefore the main object of the present invention to avoid such precambering, and instead to effect cambering simultaneously and progressively in the same localized zone and in the same operation with the heat treatment, to produce a uniform and reliable product.

According to the present invention, this compensation is provided by setting up a longitudinally progressive bending moment in the rail being heat treated, at the localized heated zone thereof. This is done by joining a plurality of rail lengths in tandem, causing relative longitudinal movement thereof with respect to a localized source of heat, and simultaneously exerting an upward force normal to the rail so as to form a longitudinally progressive localized camber in the rail at the heated zone, before the rail is quenched.

This upward force continuously lifts the weight of the rail ahead of and behind the heated zone. The distance from the upward force to the center of gravity of the cold metal ahead of and behind this upward force, is the approximate lever arm to which such rail weight is 3,266,956 Patented August 16, 1966 applied as the force to produce the desired bending moment at the heated zone.

The metal in the heated zone is softer than the cold metal ahead of and behind the same, and the resultant bending is effectively and continuously localized in the heated zone. This bending causes an elongation or stretching of the metal in the heated zone beyond the elastic limit thereof. This elongation compensates for and is taken up by the shrinkage or thermal contraction in the subsequent quenching zone, resulting in a relatively fiat rail.

The metal in the localized zone is heated to a temperature sufficient to austenitize a control-led amount of rail steel in the ball of the rail head.

Air quench is applied at a controlled rate and time interval to cause trans-formation essentially to a mixture of fine pearlite and Bainite preventing the formation of undesirable martensite. The micro structure in the hardened zone is preferably composed of primarily fine pearlite.

Rails hardened by this invention are straight, i.e., hat, to a commercially acceptable degree, and their service life is increased many fold.

In the drawings:

FIGURE 1 is a diagram showing the rail in incoming, cambering, hardening, and outgoing steps in the process;

FIGURE 2 is a plan of apparatus according to, and for carrying out, the method of the present invention;

FIGURE 3 is a side elevation of the same;

FIGURE 4 is a vertical section taken along the line 44 of FIGURE 2; and

FIGURE 5 is a vertical section taken along the line 5-5 of FIGURE 2..

As shown in FIGURE 1, rail lengths A, B, C, D and E are joined in tandem at I, and are moved continuously in the direction of the arrow shown. Heat is applied by a source H to a longitudinally progressive localized zone Z on the outer surfaces of the ball or head of the rail length B. A progressive bending moment is set up by the weight of the so connected rail lengths and by applying an upward additional force F to the rail base under the zone Z.

This force F elevates a length containing the zone, and at least a part of an adjacent tandem length. The distance from the force F to the center of gravity of the weight at each side the rails thereof thus elevated is the lever arm to which such weight is applied to produce the desired bending moment. Thus, the total bending moment is produced by both the force F and the weight of the rails. The ball of the rail is hardened from end-toend thereof by continuously eamberi-ng such rail to provide a transverse zone of steel in the ball that is elongated by tension adjacent the top of the ball, which transverse zone progressively moves with respect to and in the ball of the rail from one end to the other thereof, applying heat to such ball only in said zone sufficient to produce a fine pearlitic grain structure When the so heated steel is quenched, and quenching such zone after it is so heated, whereby the steel in ball of the rail is hardened throughout its length. r

In the position shown, the force F lifts part of the outgoing length C and a part of the incoming length A. The length A is in position to have a new untreated length joined thereto, and the outgoing length E is in position tandem along the rail. .mounted beyond the air quenches 26. The blowpipes to be removed as the product of the process. The supports S for receiving such new length are horizontal to form a convenient loading platform.

As shown in FIG. 3, upward force F is applied to a camber roll 30, along with drive rolls 10, 12, 14, 16, all higher than the loading platform so that the tandem lengths A and B, FIG. 1, are inclined upwardly with some curvature, and the incoming grade rolls I thereunder are of corresponding heights. The outgoing hardened lengths C, D and E are inclined downwardly with some curvature, and the guide rolls R thereunder are of corresponding decreasing height. The length B may leave the rolls thereunder, delivery not requiring the precision positioning needed for the loading platform S.

As also shown in FIGURE 3, the preferred apparatus employed in carrying out the process comprises a frame in which are mounted traction rollers 10, 12, 14 and 16. These rollers cooperate with hold down rollers 15 and 17 journaled in fixed hearing in the frame to form incoming and outgoing sets of power pinch rolls for propelling the successive rail lengths by traction, said traction rollers aiding the support of the rail string along with camber roll 30.

Midway between the rollers 15 and 17 and above the rail R is mounted a control panel 20. Vertically slidably mounted on the control panel are preheat blowpipes 22, hardening blowpipes 24 and air quenches 26, spaced in Cooling water sprays 28 are are preferably of the oxy-natural gas type, and their flames form the source of heat H. Below the control panel are mounted aligned camber rolls 30 journaled in levers 32 having alternate ends fulcrumed n the frame, and opposite ends linked to fluid pressure cylinders 34 and 36,

respectively. Such pressure exerts the vertical upward force F on the camber rolls 30, to partiall lift joined lengths of the rail, and along with support of the traction rolls cause a bending moment in the moving rail and stretching of the metal in the localized heated zone, and forms the resultant continuous cambering therein.

The rollers 10, 12, 14, 15, 16, 17 and 30, burners 22 and 24, quenches 26 and sprays 28 constitute a hardening unit, and relative movement between that unit and the rail longitudinally thereof is preferably caused by traction of the rolls 10 and 12, driven by respective sprocket drives from a shaft 38, and the rollers 14 and 16 from a shaft 46, both shafts being driven from a power shaft 42.

The sprocketed traction rollers are each journaled in a respective lever 44 pivoted at one end on their respective drive shafts, and linked at the other end to respective fluid pressure cylinders 46 and 48. The lifting by the camber roll 30 causes the rail on the rollers 10 and 12 to be inclined upwardly, and the rail on rollers 14 and 16 to be inclined downwardly, in the direction of movement of the rail. The cylinders 46 and 48 are accordingly adjusted to such angles and produce equal pinch pressure. The tandem relation of the traction rollers provides that when one of the rollers is on a joint, there is always another roller on the unbroken rail between the joints to insure traction.

In the form shown, the hardening unit is a stationary machine, a-nd several rails in parallel are drawn into the stationary machine, the rails being formed by sections bolted together in tandem. For convenience in tandem loading the respective parallel rails, the joints are staggered. When such joint reaches the heating station, the blowpipe for that rail is raised to avoid overheating resultant from the heat dam formed by the section end at the joint.

The rail size may be from /2 to 8 inches depth. As a specific example, a 132 1b. RE rail of 39-foot length was employed. The length between the hold down rollers was feet 6 /2 inches. The speed of the rail is from 7 to inches per minute. In the example, a speed of seven and one-fourth inches per minute was employed. The pinch rollers were 8-inch diameter, hold down rollers 5-inch diameter, camber roll 6-inch diameter. The camber pressure was psi. for an 8-inch diameter cylinder, say a vertical force of 5,000 pounds which augments the bending moment caused by the weight of rail. The hardening temperature was approximately 1600 F.

In the example, there are a plurality of tandem rail lengths in process at any one time. The length being heated is over the camber roll and under the burners with at least one incoming and one outgoing length joined thereto, preferably a total of five lengths.

The outgoing length contributes to the relatively moving camber in the length being heated, at the time when the joint thereto to oncoming end of the rail to be heated reaches the burners, while the incoming length contributes to the relatively moving camber at the time when the joint thereof to the outgoing end of the heated length leaves the burners.

Thus, there is a downward force of at least the weight of one incoming length and one outgoing length resting on the traction rolls '10, 12, 1'4 and 16 the reaction forces of said traction rolls aiding the upward force of the camber roll to produce the total bending moment. The forces resultant of these form the total bending moment in the localized heating zone below the burners.

The metal in the localized heated zone is softer than that in the cold incoming and outgoing metal, and the elastic limit of the heated metal is lowered. The effect of the bending moment of the cambering force and the stretching of the metal is therefore concentrated in the heated zone.

As the quenching heads are reached, the quenching causes progressive shrinkage and contraction in the heated metal, which takes up the elongation and thereby continuously removes the camber. The rail leaving the quenching zone is therefore straightened.

The abutment rolls locate a datum line with respect to which the incoming rails leaving the horizontal loading zone are gradually inclined upward to pass above the datum line as they pass under the abutment rolls so as to pass over the camber roll. The outgoing lengths are inclined downwardly for delivery, which does not require the degree of precision in location necessary for loading.

What is claimed is:

1. Method of thermally hardening a zone adjacent the surface of an elongated steel member, which comprises progressively heating to a hardening temperature a transverse zone adjacent such surface which zone moves longitudinally with respect to said member, while simultaneously progressively stretching the metal of the so moving zone beyond the elastic limit of the metal at said temperature, and progressively quenching the so heated metal of such moving zone to harden the metal and shrink the same to produce a relatively straight elongated member having a hard zone adjacent the surface thereof.

2. Method of hardening a surface of a steel beam, which comprises joining loading members in tandem at each end of the beam, causing relative movement of said beam and tandem members longitudinally of said beam with respect to a so-urce of heat, progressively bending the beam while applying heat from said source to a hardening temperature to a progressively localized zone of said surface to form a progressive camber in the beam, and progressively quenching said heated zone to harden said surface to shrink the same to remove said camber and produce a straightened beam.

3. Method of thermally hardening wear surfaces of the steel in the head of a rail, which comprises setting up longitudinally progressive bending movement in the rail while applying heat to a hardening temperature to a progressive localized zone o-f said wear surfaces of the head of the rail to form a longitudinally progressive localized camber in the rail, and progressively quenching said heated zone to harden said wear surfaces and. shrink the same to remove said camber and produce a straightened rail with thermally hardened wear surfaces continuous from end to end thereof.

4. Method of thermally hardening a zone of steel in the head of a rail, which comprises causing relative movement longitudinally of said rail between said rail and a source of heat, simultaneously applying heat from said source to a localized zone of adjacent the top surface of said relatively moving :rail to heat said layer progressively to a hardening temperature, simultaneously applying quenching medium to said heated zone in tandem to said heat application to progressively harden the metal, and simultaneously applying normal to the bottom flange of said rail at a point opposite to said zone of heat application a force suflicient to cause a progressive camber in said rail to substantially equalize the force of thermal contraction.

5. Method of thermally hardening a zone of steel in the head of a rail, which comprises joining a plurality of rail lengths in tandem, causing relative movement longitudinally thereof with respect to a source of heat, simultaneously applying heat from said source to a localized zone adjacent the top surface of said relatively moving rail to heat said layer progressively to a hardening temperature, simultaneously applying quenching medium to said heated zone in tandem to said heat application to progressively harden the metal, and simultaneously exerting an upward force normal to the rail below said source of heat to lift the length of rail being heated and at least a portion of a length tandem thereto so as to form a progressive localized camber in the rail and stretch the metal in said heated zone sufficient to substantially equalize shrinkage.

6. Method as claimed in claim 5, in which the application of heat to the relatively moving rail is decreased as the joint reaches the heat source until the joint has passed the heating zone to avoid overheating of the section ends at said joint.

7. Method as claimed in claim 6, in which a plurality of such jointed rails are treated simultaneously in parallel relation, and the joints thereof are staggered longitudinally of the rails.

8. Method of thermally hardening a zone only the top and side surfaces of the head of a steel rail and a small substantially uniform thickness of the steel therebelow, which comprises pas-sing said rail longitudinally over a camber roll, exerting an upward pressure on said camber roll to cause a camber in said moving rail, applying heat toward said surfaces from a source spaced therefrom to heat said surfaces and steel thickness to a hardening temperature, applying quenching medium toward said surfaces from a source spaced from said top surface and longitudinally from said heat source, and maintaining said sources and the axes of said rolls all stationary relative to each other to form a hardening unit, causing relative movement between said unit and said rail longitudinally of said rail and thereby progressing said camber, said heating, and said quenching longitudinally of said rail, said pressure applied to said camber roll being suificient to substantially equalize the force of thermal contraction resultant from the quenching of said heated thickness of steel.

9. Apparatus for thermally hardening a zone adjacent the surface of an elongated steel member which comprises means for progressively heating to a hardening temperature a progressive localized zone of metal adjacent said surface, means for simultaneously stretching the metal of said surface beyond the elastic limit thereof at said temperature, and means for progressively quenching said heated zone to harden the metal and shrink the same to take up such stretch producing a relatively straight elongated member, in which such zone adjacent said surface is relatively hard.

10. Apparatus for thermally hardening a zone adjacent the sunface of a steel beam which comprises means for progressively bending the beam to form a progressive chamber in the beam, means for heating to a hardening temperature a progressively localized zone adjacent said surface and means for progressively quenching said heated zone to harden said surface to shrink the same to remove said camber, producing a relatively straight beam, having a hardened elongated zone along such surface.

11. Apparatus for thermally hardening a zone adjacent the wear surfaces of the head of a steel rail, which comprises means for setting up a longitudinally progressive bending moment in the rail to form a longitudinally progressive localized camber in the rail, mean-s for simultaneously heating to a hardening temperature a progressive localized zone adjacent said wear surface and means for progressively quenching said heated zone to harden the metal and shrink the same to remove said camber producing a relatively flat rail with a thermally hardened zone adjacent such wear surfaces extending from one end to the other end of said head.

12. Apparatus for thermally hardening a zone adjacent the top of the head of a steel rail, which comprises a source of heat, means for causing relative movement longitudinally of said rail between said source of heat and said rail, means for simultaneously applying heat from said source to a localized zone of the top surface of said relatively moving rail to heat the metal of such zone progressively to a hardening temperature, means for simultaneously applying quenching medium to said heated top surface in tandem to said heating means to progressively harden said metal, and means for simultaneously applying normal to the bottom flange of said rail at a point opposite to said source of heat a force sufficient to cause a longitudinally progressive camber in said rail to substantially equalize the force of thermal contraction of quenching said heated layer.

13. Apparatus for thermally hardening a zone adjacent only the top and side surfaces of the head of a steel rail and a small substantially uniform thickness of the steel therebelow, which comprises a camber roll engaging the bottom of said rail, means for exerting an upward force on said camber roll to cause a camber in said rail, means for applying heat toward said surfaces from a source spaced therefrom to heat the steel in said zone to a hardening temperature, means for applying quenching medium to said surfaces from a source spaced from said top surface and longitudinally from said heat source, a hardening unit in which said sources and the axes of said rolls are mounted, and means for causing relative movement between said unit and said rail longitudinally of said rail and thereby progressing said camber, heating and quenching longitudinally of said rail, said upward force on said camber roll being sufficient to substantially equalize the force of thermal contraction resultant from the quenching of said heated thickness of steel.

14. Apparatus as claimed in claim 13, in which said hardening unit comprises a pinch roll, and said relative movement causing means applies traction between said rail and one of said rolls.

15. Apparatus as claimed in claim 13, in which a plurality of parallel rails are positioned between said camber roll and said opposing rolls, and said hardening unit comprises a separate heat source and quenching source for each of said parallel rails.

16. Rail thermally hardening machine Icomprising a frame, a pair of spaced apart hold down rolls journaled in said frame, pinch rolls cooperating with said hold down rolls [to receive a plurality of parallel rails therebetween, means for driving said pinch rolls to propel the rails longitudinally therethrough by traction, camber rolls respectively engaging the bottoms of each of said rails and centered between said hold down rolls, said frame supporting in tandem above each rail and camber roll a preheat head, a heating head, a quenching head, and means for moving said camber rolls upwardly to bend the heated rails.

'7 17. Method of hardening the ball of a steel rail from end-to-end thereof, which comprises continuously cambering such rai l as the same is being heated to provide a transverse zone of steel in the ball that is elongated by tension adjacent the top of the ball, which transverse zone progressively moves with respect to and in the ball of the rail from one end to the other thereof, applying heat to such ball only in said zone sufficient to produce a fine pearlitic grain structure when the so heated steel is quenched, and quenching such zone after it is so heated, whereby the steel in ball 0f the rail is hardened throughout its length.

References Cited by the Examiner UNITED STATES PATENTS 2,254,307 9/1941 Mott et al. 148151 8 2,570,883 10/1951 Stivin l48-13l 3,124,492 3/1964 Dewez et a1. 148-431 X 3,193,270 7/1965 DeWez et a1. 2665 References Cited by the Applicant UNITED STATES PATENTS 2,049,830 8/ 1936 Bayless. 2,570,883 10/1951 Stivin.

FOREIGN PATENTS 112,784 4/ 1941 Australia.

DAVID L. RECK, Primary Examiner.

C. N. LOVELL, Assistant Examiner. 

5. METHOD OF THERMALLY HARDENING A ZONE OF STEEL IN THE HEAD OF A RAIL, WHICH COMPRISES JOINING A PLURALITY OF RAIL LENGTHS IN TANDEM, CAUSING RELATIVE MOVEMENT LONGITUDINALLY THEREOF WITH RESPECT TO A SOURCE OF HEAT, SIMULTANEOUSLY APPLYING HEAT FROM SAID SOURCE TO A LOCALIZED ZONE ADJACENT THE TOP SURFACE OF SAID RELATIVELY MOVING RAIL TO HEAT SAID LAYER PROGRESSIVELY TO A HARDENING TEMPERATURE, SIMULTANEOUSLY APPLYING QUANCHING MEDIUM TO SAID HEATED ZONE IN TANDEM TO SAID HEAT APPLICATION TO PROGRESSIVELY HARDEN THE METAL, AND SIMULTANEOUSLY EXERTING AN UPWARD FORCE NORMAL TO THE RAIL BELOW SAID SOURCE OF HEAT TO LIFT THE LENGTH OF RAIL BEING HEATED AND AT LEAST A PORTION OF A LENGTH TANDEM THERETO SO AS TO FORM A PROGRESSIVE LOCALIZED CAMBER IN THE RAIL AND STRETCH THE METAL IN SAID HEATED ZONE SUFFICIENT TO SUBSTANTIALLY EQUALIZE SHRINKAGE. 